1. Field of the Invention
The present invention relates to a shielding device for a connector unit, such as a card bus connector, and the connector unit using the same, and particularly to a shielding device which provides the related connector unit with satisfactory effects of noise suppressing, stable transmission, and particle isolation.
2. The Prior Art
Noise inevitably exists during signal transmission between electrical devices connected by wires and connectors. The noise may result from electrostatic discharge (ESD) or electromagnetic interference (EMI). ESD exists on two device surfaces when sufficient particles settle thereon thus forming an electrostatic capacitor between the two devices which emits electrostatic electrons that interfere with the performance of the related devices and other peripherals. When two mating devices, such as an electrical card and a related card connector are abruptly connected together in a relatively dry environment, particles on the devices may cause an electrostatic discharge and damage the components within the electrical card. Noise can also result from EMI which is related to an electrical current flowing through the devices. Prior art which prevent noise from affecting the card connector include U.S. Pat. Nos. 5,288,247, 5,470,259 and 5,478,260. However, these disclosures only provide a front shielding to cover a front edge of the connector where soldering portions of the contacts are to be soldered on a printed circuit board. No shielding is provided to cover the guiding frame of the connector, thus the noise problem still exists due to insufficient shielding protection of the card connector. If an electrical card and a reception interface of the card connector are not sufficiently isolated or protected by a metal shield, these portions will be adversely affected by EMI. Additionally, dust is apt to gather on the card-connector assembly due to an insufficient metal shield thus causing ESD. Moreover, heat dissipation is a problem encountered in the PC field for meeting the high power and high frequency trend of signal transmission.
Therefore, an improved shielding device for a card connector is required to eliminate the above mentioned drawbacks of the prior art especially one which can considerably eliminate problems resulting from ESD and EMI.